THE AORTA AND PULMONARY ARTERIES IN FALLOT'S TETRALOGY

Abstract
In Fallot''s tetralogy, the ascending aorta is enlarged but it narrows rapidly at a point immediately distal to the origin of the left subclavian artery. Owing to the dextroposition of the aortic root and the shape of the ascending aorta the ascending and descending limbs of the arch are more widely separated than in the normal structure. In instances where pathology is associated with a right-sided aortic arch, the descending aorta usually crosses to the left of the midline in the lower 3 of the thorax. An anomalous retroesophageal right subclavian artery occurred in 14% of 60 cases of Fallot''s tetralogy, compared with a frequency of about 0.7% in the population as a whole. In about 33% of cases, there was an unequal division of the pulmonary trunk and in the majority of these instances, the left pulmonary artery was the larger branch. Unequal size of the pulmonary arteries was not sufficient to cause any difference in opacification of the periphery of the lung fields.